Telemetric gages



Aug. 16, 1955 H. E. TATEL ETAL 2,715,680

TELEMETRIC GAGES Filed March 22, 1950 2 Sheets-Sheet 1 FIG! 1 2 INVENTORS. HOWARD E. TATEL EDGAR W. TRAINER AT TORN E Y g- 16, 1955 H. E. TATEL ET AL 2,715,680

TELEMETRIC GAGES Filed March 22, 1950 2 Sheets-Sheet 2 INVENTORS. HO WARD E. TATEL BY DG R W. TRAINER ATTORNEY rELnMErnrc GAGES Eon/2rd E. Tatel, Silver Spring, Md, and Edgar W. Trainer, Rcchester, N. Y., assignors to the United States of America as represented by the Secretary of the Navy Appiication March 22, 1950, Serial No. 151,104

9 Claims. (Cl. 250-36) The present invention relates in general to an improved telemetric instrument, and more specifically to a device for providing signals indicative of pressures, accelerations and other phenomena.

In the design of rocket and ram jet projectiles, experimental models are built and test-flown. To achieve the best design a knowledge of the pressures acting at various points, both external and internal, on the models while in flight is necessary. it is also necessary to know both the acceleration produced by the rocket or ram jet and the resistance of the air to the passage of the projectile. This air drag can be computed from the negative acceleration it causes.

One of the principal objects of the present device is to provide a pressure gage, carried by the projectile, which will produce information concerning pressures on the projectile for transmission to a remote location by means of a suitable radio transmitter also mounted in the projectile.

Another object of the invention is to provide a gage which will produce information concerning the acceleration, positive or negative, of the projectile.

A further object of the invention is to provide a gage suitable for installation in a projectile and consisting of relatively few parts of simple design.

Other objects and many of the attendant advantages of this invention will be appreciated readily as the same becomes understood by reference to the following de tailed description, when considered in connection with the accompanying drawings, wherein:

Fig. i is an elevation of a gage embodying the invention, with the outer casing partly broken away;

Fig. 2 is an axial section through the gage, when connected to measure pressures exceeding that of the atmosphere;

Fig. 3 is a fragmentary axial section showing the lower end of the gage, when connected to measure sub-atmospheric pressures;

Fig. 4 is a view similar to Fig. 3, but showing the connections used for measuring differential pressures;

Fig. 5 is a circuit diagram showing how the gage may be connected to the oscillator of an associated radio transmitter;

Fig. 6 is an axial section through a modified gage arranged for measuring acceleration, either positive or negative;

Fig. 7 is a partly sectional elevation thereof with the movable parts in slightly altered positions;

Pig. 8 is a perspective view of a supporting spring forming part of the gage of Figs. 6 and 7; and

Fig. 9 is perspective view of a modified spring.

Referring first to Figs. 1 and 2, there is shown a casing 10 in which ishoused a metal bellows 11 of the Sylphon type, which has its upper end 12 closed, and is secured in pressure-tight relation to the stud 13 at its lower end. A helical spring 14 is enclosed in the bellows 11 and at its lower end bears against a shoulder 15 on the stud, while its upper end bears against a companion shoulder rates Patent Patented Aug. 16, 1955 16 on an abutment head 17, which in turn rests against the inner surface of the bellows end 12.

The stud 13 is supported by or integral with the lower head 18 which fits in the bottom of casing 10 and may be held in place by the flange 19, which is crimped or otherwise secured around its edge. A shallow cup-shaped member 2%) of material of good magnetic permeability, such as Permalloy or Mu-metal, is secured to the outside of the upper end of the bellows, an intermediate threaded fitting 21 being shown as one way of holding the said member 2% in place. For brevity, this member 20 is hereinafter called an armature. Obviously other means of securing the same are permissible, provided a firm connection is made, so that the armature 20 will move with the bellows end 12.

A bore 22 is provided in the stub 13, in communication with a larger threaded bore 23, which in the present instance is closed by a screw 24 with a sealing gasket 25 under its head, to make a pressure-tight joint. A second bore 26 passes through the lower head 18, and is likewise threaded. As shown, it receives a correspondingly threaded inlet fitting 27, having conventional annular ribs on its outer surface to be received in a rubber tube or other pressure conduit.

Above the armature 2% is a magnetic core consisting of a cylindrical element 23, preferably made of compacted comminuted magnetic material, and having an annular channel 29 to receive two coils or windings 3i) and 31 respectively. These coils are shown connected to the four terminals 32, 33, 34 and 35. A suitable insulating spool 36 supports the coils, which may be wound on said spool and then inserted in the annular channel 29 and secured in place. The core 28 is mounted in the upper head 37, which is made of insulating material and is shaped as an inverted cylindrical cup, that fits in the casing It A cylindrical spacer 38 fits between the lower edge of upper head 37 and the upper edge of lower head 18. A flange 39 at the upper end of casing 19 bears against the upper end of head 37. The whole is fitted closely, so that the chamber within the casing and its contents are sealed pressure-tightly against the exterior, except through the bores specifically provided for communication with said chamber.

In the form just described, and illustrated in Figs. 1 and 2, the device is suitable for measurement of pres sures in excess of atmospheric pressure. When fluid at such super-atmospheric pressure is admitted through the fitting 27, it exerts a pressure on the outside surface of the bellows 11, tending to collapse the latter against its own resistance and that of the spring 14, as well as the pressure of the air within the bellows.

When the fitting 27 is placed in the central bore 23 and the bore 26 is closed by the screw 24 as shown in Fig. 3, the pressure fluid entering through said fitting 27 will act on the inner surface of the bellows, while the outer surface of said bellows will be at the substantially constant pre-set pressure, for example, atmospheric pressure, originally existing within the casing 1d, and if now a subatmospheric pressure is applied through the fitting 27 said external pressure on the bellows will cause the latter to contract and move the armature 2i) downward.

Finally, in the arrangement shown in Fig. 4, a fitting 27 is applied to bore 23 and a similar fitting 27a to bore 26, whereby two different pressures may be conveyed simultaneously to the inner and outer surfaces respectively of the bellows, so that the device then acts as a differential pressure gage. Obviously, if the initial position of the bellows is as illustrated in Figs. 1 and 2, the higher pressure should be applied to fitting 27a.

Referring now to Fig. 5, there is shown one way in which the device may be used in telemetry. A thermionic tube 4%, here shown as a triode, is provided to act as an audio frequency oscillator. The terminal 35 of coil 31 is connected to the cathode 41 of tube 40 while the other terminal 33 of said coil 31 is connected to the control grid 42. The terminal 32 of coil 30 is connect ed to the positive terminal of the source of anode energization through a resistor 44, while the other terminal 34 of said coil is connected to the anode 43 through a resistor 45. A capacitor 46 is connected between terminals 32 and 35 and a second capacitor 47 is connected between terminals 33 and 34. A third capacitor 43 is connected in series in the output lead of the osciliator, as shown. The cylindrical magnetic element or core 28 is indicated diagrammatically as a core common to both coils, while the variable inductance of the coils is shown by the arrows 49 and 59. The inductance of each of the coils increases or decreases simultaneously as indicated by the dashed line 51. The movable variable inductance means actually consists of the armature 20, the variation being due to the shifting of said armature toward and away from the core 28.

Passing now to the modified gage shown in Figs. 6 and 7, the general appearance is much the same as that of the forms just described, but there is no external pressure connection. As in the said prior-described forms, there is a casing which however is here shown as a cup 52 that is one-piece at its lower portion, with a conical bore 53 terminating in a threaded opening 54 closed by a screw plug 55, for use in introducing fluid.

Resting on a shoulder 56 is the rim of a spring 57 of spiral type, which will be described later. Abutting the upper edge portion of this spring is a cylindrical spacer 58 upon which rests a similar spring 57 and in turn a second, shorter, spacer 59. Abutting the upper end of spacer 59 is the upper head 37, identical in structure and function with that shown in Figs. 1 and 2 and previously described. The contents of this head, consisting of elements 28, 29, 30, 31, and 36 are likewise identical with those in Figs. 1 and 2, as are also the terminals 32, 33, 34 and 35.

However, the magnetic member or armature 60, which replaces armature 29 of the other form, is made of somewhat dilferent shape and instead of being cup-shaped, is here a disk with a threaded central lug 61 which receives a threaded stud 62. This stud passes centrally through the upper spring 57 and is then screwed into the upper end of the bore 63 of a tubular spacer 64, whose lower end rests on the central portion of the lower spring 57. A screw 65 passes centrally through said lower spring and is screwed into the lower threaded bore 66 of the spacer 64.

The detailed structure of each spring 57 is shown in Fig. 8. It will be noted that the outer edge portion or rim 67 of the spring is an unbroken ring and that transverse resiliency is secured by cutting a spiral slot 68 from a point near the periphery to a point near the central hole 69. The portion 70 surrounding said hole, like the outermost portion, is also an unbroken ring. Thus firm seats are provided at the edge and center of the spring, to hold the spring securely at said locations.

The spring 57 can yield as shown in Fig. 7, the outer edge portion remaining stationary and the center moving downward. The two identical springs 57 thus provide a parallel-motion guide for the spacer 64 and the armature 60 mounted thereon, whereby the upper surface of said armature 60 remains parallel to the under surface of the cylindrical magnetic core 28, whenever relative motion occurs.

The spring 77 shown in Fig. 9 is an alternative form which may be used instead of spring 57 if preferred. Like spring 57, it has an unbroken peripheral portion 76, a central aperture 71 and an unbroken central portion 72 surrounding said aperture, but unlike spring 57 it has two spiral slots 73 and 74, placed symmetrically and providing somewhat better-balanced forces, that permit increased transverse yield without producing misalinement of the spacer 64 and the armature 60 mounted thereon.

A filling of suitable damping liquid 75 is placed in the casing 52, and the slot or slots in the springs allow said liquid to flow past said springs when motion occurs.

The operation of the various forms of the invention will now be described.

When the gage shown in Figs. 1 and 2 is to be used as a telemetric pressure gage, the device is installed in a suitable location in the projectile, the fitting 27 is connected by a tube to the point on the interior or exterior of the projectile where pressure measurement is desired, and the coils 30 and 31 are connected to form part of the tank circuit of an audio-frequency oscillator, for example, as shown in Fig. 5. Pressure is applied through the tube to the exterior of the bellows 11, compressing it against the combined resistance of the spring 14 and the bellows, and drawing the armature 20 away from the pole faces of the core 28. As the armature 20 is withdrawn from the core, both the individual inductances and the mutual inductance of the coils 30 and 31 are decreased, that is, both inductance and coupling decrease. The said decrease bears a definite relationship to the pressure applied and is employed to raise the frequency of the output of the audio-frequency oscillator which, in turn, modulates the carrier frequency of an associated radio transmitter, not shown, carried by the test projectile. Hence, the frequency of the signal heard at the radio receiver is indicative of the pressure at the chosen point on or in the projectile under test.

When the same gage is to be used to measure subatmospheric pressures, as in Fig. 3, the fitting 27 is connected by a tube to the point of low pressure on the surface of the projectile, with the result that the pressure within the bellows 11 is reduced below that in the chamber surrounding the bellows and the compression thereof and withdrawal of the armature 20 from the core 28 are proportional to the diiference in pressure so established. This serves to produce the indicating signal as hereinbefore described.

When the device is to be used as a differential gage, as shown in Fig. 4, fitting 27a is connected by a suitable tube to a point of higher pressure on the projectile and the fitting 27 is similarly connected to a point of lower pressure thereon. The result of this is that the higher pressure tends to compress the bellows 11 while the lower pressure tends to extend it and thus the effective resultant pressure acting on the bellows to compress it against its own resistance and the resistance of the spring 14 is the difierence between the higher pressure acting on its exterior and the lower pressure acting on its interior, whereby the movement of the armature 26 becomes a function of the said difference in pressures. The information is transmitted by radio, as in the preceding forms.

The operation of the acceleration gage shown in Figs. 6 and 7 is as follows: The gage is mounted with its axis parallel to that of the projectile and with the end carrying the plug away from the direction in which the positive or negative acceleration is to be measured. The coils 30 and 31 are connected, as shown in Fig. 5, to form part of the tank circuit of the audio-frequency oscillator. As the acceleration affects the projectile, and through it, the case 52, core 28 and coils 30 and 31 of the device, the inertia of the armature and its stem 64, considered as a unit, acts to move said armature away from the pole faces of the core 28 against the resilient resistance of the springs 57, and the motion is smoothed and damped by the liquid 75. This increased separation decreases the inductance of the coils 30 and 31. The decrease in inductance bears a definite relationship to the increase in the value of the acceleration or deceleration of the projectile. It is possible, therefore, to employ the change in inductance to control the output of the radio transmitter in the manner hereinbefore described so that the received signal is indicative of the acceleration or deceleration of the projectile.

In deceleration measurements the indicated deceleration provides the information from which the air drag may be computed. I

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. In a telemetric gage, a case, a recessed base closing the case at one end thereof, a core of magnetic material in the base said core having an E-shaped longitudinal section, a pair of coils wound on the center leg of said core, an armature in the case, resilient means normally engaging the armature with the center and outside legs of said core, means for transmitting forces to said armature for shifting said armature in a direction away from the core to change the inductance and coupling of the coils, and damping means retarding movement of said armature.

2. A telemetric gage as recited in claim 1, wherein said damping means comprises a viscous liquid.

3. A telemetric gage including a case open at one end,

a base closing the case at said open end and having a recess therein, a recessed, magnetically permeable core fitted in the base, the recess in said core providing an E-shaped longitudinal section, a pair of coils in the recess of said core, an armature in the case having a stem, a spring resiliently connecting said stem with the case, and a damping fluid carried in the case, said armature being shiftable by axial forces of acceleration or deceleration away from the core against the tension of said spring and said damping medium for changing the inductance of said coils.

4. An instrument for use in telemetry, including a pair of coils, a magnetic core having an E-shaped longitudinal section on the center leg of which both the coils are wound in superimposed relationship, an armature positioned adjacent the outside legs of said core, spring means normally retaining the armature in abutting relationship with the legs of said core, a pressure-tight casing forming a chamber enclosing said coils, core, armature and spring retaining means, and means within the chamber and connected to said armature for displacing the armature in response to an external stimulus in a direction away from the core to reduce the inductance of both of said coils.

5. In a telemetric gage having a variable frequency oscillator, a pickup unit comprising a pair of coils which are connected as the plate and grid inductances of the oscillator, a magnetic core having an E-shaped longitudinal section on the center leg of which said coils are wound in superimposed relationship, an armature movably mounted adjacent the outside legs of said core, means normally retaining the armature close to the core, a casing forming a pressure-tight chamber enclosing said coils, core, armature and retaining means, means for introducing pressure into said chamber, and expansible means within the chamber for displacing the armature with respect to the core under the influence of said pressure to vary the inductance of the coils.

6. In a telemetric gage having a variable frequency oscillator, a pickup unit comprising a pair of coils which are connected as the plate and grid inductance of the oscillator, a magnetic core having an E-shaped longitudinal section on the center leg of which core both of said coils are wound in superimposed relationship, an armature movably mounted adjacent the outside legs of said core, means normally retaining the armature in engagement with the core, a casing forming a pressure-proof enclosure about said coils, core, armature and retaining means, a flexible partition dividing said enclosure into chambers, said partition being linked with said armature and shiftable for moving the armature toward or away from the legs of said core, and means for introducing fluids at different pressures into the chambers on the opposite sides of the partition to create difierential forces for moving said armature and thereby alter the frequency of the oscillator.

7. In a telemetric gage having a variable frequency oscillator, a pickup unit comprising a pair of coils which are connected as the plate and grid inductances of the oscillator, a magnetic core having an E-shaped longitudinal section on the center leg of which said coils are wound in superimposed relationship, an armature movably mounted adjacent the legs of said E-shaped core, means normally retaining the armature in engagement with the legs of said core, a case forming a pressure-proof enclosure about said coils, core, armature and retaining means, a flexible partition dividing said enclosure into chambers and connected to said armature for moving the armature toward or away from the core, and means for introducing fluid at low pressure into one chamber, so that normal fluid pressure in the other chamber tends to move the armature away from the core, whereby the introduction of said low-pressure fluid allows normal fluid pressure to move the armature for varying the inductance of the coils.

8. In a telemetering gage, a cylindrical case, a recessed head closing the case at one end thereof, a core of mag netic material mounted in the head, said core being recessed to provide a central leg, a pair of coils wound in the recess of said core in superimposed relationship upon the central leg of said core, an armature movably mounted in the case and positioned adjacent the recessed portion of said core, spring means carried in said case and normally retaining the armature in abutting relationship with the core, means closing the other end of the case to form a pressure-tight chamber within said case, and expansible means carried in the chamber and connected to said armature for displacing the armature in response to an external stimulus in a direction away from the core to reduce the inductance of the coils.

9. In a telemetering gage, a variable frequency generator comprising a vacuum tube oscillator, said tube having a plate connected to a source of potential, a grid, and a cathode, a first inductance coil connected in the plate circuit of said tube, a second inductance coil connected between the grid and cathode of said tube, a magnetic core having an E-shaped longitudinal section on the center leg of which both coils are wound in superimposed relationship, an armature movably mounted adjacent the outside legs of said core, spring means normally retaining the-armature in abutting relationship with the core, a pressure-tight casing forming a chamber enclosing said coils, core, armature and spring retaining means, and expansible means within the chamber connected to said armature for displacing the armature in response to an external stimulus to vary the inductance of the coils and the frequency of the oscillator.

References Zited in the file of this patent UNITED STATES PATENTS 1,343,562 Heising June 15, 1920 1,585,244 Hoflman May 18, 1926 1,944,988 Lum Jan. 30, 1934 2,234,184 MacLaren Mar. 11, 1941 2,332,565 Fairbank Oct. 26, 1943 2,375,911 Foster May 15, 1945 2,417,097 Warshaw Mar. 11, 1947 2,436,639 Faus Feb. 24, 1948 2,466,071 Barnes Apr. 5, 1949 2,494,621 Jones Jan. 17, 1950 2,510,073 Clark June 6, 1950 2,515,969 Shibers July 18, 1950 2,607,220 Martin Aug. 19, 1952 2,692,501 Erwood Oct. 26, 1954 

